A major segment of the aggregate industry employs Vertical Shaft Impact (VSI) crushers to reduce large earth materials to smaller sized aggregate. VSI crushers rely on centrifugal force to disperse large aggregate through the crusher, and to impact the aggregate against a wide variety of impact crusher components to break up, reduce in size, and ultimately eject from the crusher, aggregate composed of desired shapes, sizes and consistency. Movement of abrasive materials such as aggregates through equipment causes abrasion and fatigue which wears out many components of the equipment. Efforts have been devoted to improvements in the design and construction of components of impact crushers to reduce the cost of acquiring and operating crushers, to enhance wear resistance of the component parts of crushers, and to facilitate rapid replacement of worn parts of crushers to enable the user of crushers to lose the least possible amount of time during which a crusher is inoperative due to worn parts.
The main components used to crush aggregate in a VSI crusher are impellers and anvils. An impeller of an impact crusher rotates to receive and hurl aggregate against one or more crusher components generally known in the art as anvils. This reduces the size of the aggregate and causes significant wear on impellers and faces of anvils.
Many in the industry have attempted to combat wear of impellers and anvils by protecting these components with hardened material. The cost of most hard materials, such as tungsten carbide, makes it cost prohibitive to make an entire anvil or impeller from this material. For this reason, only surfaces exposed to the abrasion contain hard material while the remainder of the piece is made of less expensive material such as steel or cast iron. U.S. Pat. No. 7,028,936, having the same inventor and assignee as the current application, suggests casting carbide bars into an air-hardened steel alloy base. U.S. Pat. No. 5,954,282 to Briske suggests threading separate wear bars into a base. U.S. patent application Ser. No. 09/921,430 teaches press fitting separate wear bars into a base.
However, in these designs, gaps remain between the wear resistant surfaces so that the milder base surface is still exposed to abrasion. This can result in what is commonly termed “wash out”. Wash out occurs when so much of the base surface has been eroded that it can no longer support the wear resistant piece. This causes the wear resistance piece to be dislodged from the base leaving the softer base material exposed to quick abrasion.
The present invention has been developed in view of the foregoing.